1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD having a color filter substrate with an identification mark.
2. Description of the Related Art
The cathode-ray tube (CRT) was developed and is mainly used for the display systems. However, the flat panel display is beginning to make its appearance due to the demand for small dimension, low weight and low voltage power consumption. At present, the thin film transistor-liquid crystal display (TFT-LCD) having a high resolution has been developed.
In general, LCD devices have various advantages in that, for example, they are thin and require low power, when compared to the CRT display devices. Therefore, such LCD devices might be good candidates to replace CRT display devices and have been a matter of great interest in some industry fields.
FIG. 1 is a schematic view illustrating a typical liquid crystal display (LCD) device. As shown in FIG. 1, the LCD device 11 includes upper and lower substrates 5 and 22 and an interposed liquid crystal material 14. The upper substrate 5, referred to as a color filter substrate, includes color filters 7, a black matrix 6 and a transparent common electrode 18 formed on the color filter 7. The color filter 7 and the black matrix 6 are positioned in the same layer between the upper substrate 5 and the transparent common electrode 18. The lower substrate 22, referred to as an array substrate, includes pixel regions xe2x80x9cPxe2x80x9d defined by the gate and data lines 13 and 15, pixel electrodes 17 formed on the pixel regions xe2x80x9cPxe2x80x9d, gate lines 13 arranged in a transverse direction, data lines 15 arranged in a perpendicular direction to the gate lines 13, and thin film transistors (TFTs) xe2x80x9cTxe2x80x9d arranged near the crossing of the gate and data lines 13 and 15 in a matrix type. The pixel electrodes 17 are made of a transparent conductive material such as ITO (indium-tin-oxide). As described, the color filter layer is formed on the upper substrate and serves to display full color.
FIG. 2 is a schematic plan view illustrating a conventional color filter substrate. As shown, the color filter substrate 31 comprises a transparent substrate (not shown), a black matrix 33, an overcoat layer (not shown), a transparent common electrode (not shown) and color filters 35 that are red xe2x80x9cRxe2x80x9d, green xe2x80x9cGxe2x80x9d and blue xe2x80x9cBxe2x80x9d. In general, the overcoat layer is formed between the color filters and the transparent common electrode. The component elements of the color filter substrate are optional in accordance with the LCD device type and operating mode. One pixel of the color filter is generally hundreds of square micrometers and a human being can not recognize it. Accordingly, the color filter is called a micro color filter.
The color filters 35 are formed from organic substances. The method of forming the color filters for use in a TFT-LCD device is classified into a dyeing method and a pigment dispersion method in accordance with the type of organic substance. Moreover, the method of forming the color filters is also classified into a dyeing method, a dispersion method, an electro-deposition method and a printing method. However, the pigment dispersion method is most widely employed in fabricating the color filters.
The black matrix 33 is generally positioned between color filters 35 having red, green and blue colors. The black matrix 33 includes portions corresponding to portions of the array substrate (see 22 of FIG. 1) that adhere to the color filter substrate when assembling the pair of substrates. The black matrix 33 is also used for shielding the reverse tilted domain formed around the pixel electrode in an in-plane switching LCD device, for example. Moreover, the black matrix 33 shields the TFT (see xe2x80x9cTxe2x80x9d of FIG. 1) from the light to minimize leakage current in the TFT. A metal thin film such as chrome having an optical density more than 3.5 and a carbon-base organic material are mainly used for the black matrix 33. A double-layer black matrix, for example, chrome/chrome oxide (Cr/CrOx) is used to lower the reflection of the LCD device screen.
The color filter substrate 31 described above is aligned and assembled with the array substrate (see element 22 of FIG. 1). In order to assemble and align the color filter substrate 31 with the array substrate, alignment keys are formed on the color filter substrate and on the array substrate at the same position. Thus, an accurate alignment of the color filter substrate and the array substrate is obtained using the alignment keys. The alignment key 37 is formed on the color filter substrate 31 when patterning the black matrix 33.
However, when fabricating the LCD device with the color filter substrate 31 and the array substrate (see 22 of FIG. 1), information about the color filter such as the manufacturing company and/or the color filter type can not be identified after the scribing and cutting steps. If a defect is found in the color filter substrate, additional steps for confirming and identifying the color filter are thus required in order to send the color filter substrate back to the manufacturer. Accordingly, productivity becomes poor and the yield is lower.
Moreover, the color filter type among the various types is chosen depending on the operation mode, and the color filter is not identified during the fabrication process of the LCD. If a wrong type of color filter is used, a complicated and labor intensive work is needed to confirm and identify the color filter after completing the LCD device.
Accordingly, the present invention is directed to a color filter substrate having an identification mark that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is a method of fabricating a color filter substrate having an identification mark for use in a liquid crystal display (LCD) device.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from that description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method of fabricating a color filter substrate for use in a liquid crystal display device includes forming a black matrix on a substrate, the black matrix having a identification mark and an alignment key; forming patterns for color filters in the black matrix; and forming red, green and blue color filters in the patterns of the black matrix.
The black matrix is made of chrome (Cr) or a resin including carbon. The identification mark includes a sign or a symbol such as characters or numbers. The sign denotes a manufacturer, a color filter type, a fabricating method and/or type of black matrix. Moreover, the identification mark and the alignment key are formed at periphery of the substrate.
In another aspect of the present invention, a color filter substrate for use in a liquid crystal display device includes a substrate; a black matrix formed on the substrate; red, green and blue color filters; and an identification mark formed at a periphery of the substrate. The color filter substrate further includes an alignment key formed at a periphery of the substrate. The identification mark is formed by patterning the black matrix.
In another aspect of the present invention, a method of fabricating a liquid crystal display device, the method comprises forming a black matrix on a first substrate, the black matrix having an identification mark at a periphery of the first substrate; forming a pattern in the black matrix corresponding to color filters; forming the color filters in the pattern of the black matrix; forming a transparent conductive layer over the color filters; and assembling the first substrate to a second substrate.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.